The cranium and mandible of the rat are observed by drawings and photographs at successive postnatal ages and, in a separate series, by alizarian vital staining and photographs of sections. This combination of methods affords comprehensive demonstration of the development of individual bones, of skeletal composites and of the skull as a whole. This process of review of this volume by comparative developmental anatomists continues. We hope to receive their criticisms and, correspondly, adapt the publication prior to October 1, 1978.